cephfs-shell: fixing TestShellOpts in test_cephfs_shell.py

cephfs-shell: fixing TestShellOpts in test_cephfs_shell.py

The issue arose due to the change in the output format of the
command `set editor`. Earlier the output format was like:
`editor: 'vim' ` which has been changed to:
```Name    Value                           Description
====================================================================================================
editor  vim                             Program used by 'edit' ```

Due to which fetching the list using indexes was `out of range`.

Introduced by: https://github.com/python-cmd2/cmd2/pull/1269/commits/fd38e706e33ff382a403e8b6956a9c1d24995ed0
Fixes: https://tracker.ceph.com/issues/63699
Signed-off-by: Neeraj Pratap Singh <neesingh@redhat.com>
(cherry picked from commit 118ac67dffdd686592dabd956ff1d285638e053e)